1. Field:
This disclosure is concerned generally with plastic bags and specifically with externally manipulated frangible valves useful in closed blood bag systems.
2. Prior Art:
Closed blood bag systems include blood bags capable of holding blood and blood components which can be externally manipulated without jeopardizing the sterility of the bag contents. Although such systems may include a single blood bag and one or more attached plastic tubings, such systems may also include several bags connected via plastic tubing which serves as a conduit for transferring blood or blood components from one bag to another. Such connected bags are well known. See, for example, U.S. Pat. No. 2,702,034 to Walter and U.S. Pat. No. 3,110,308 to Bellamy. As used herein, the expression closed blood bag system includes such single bags and such connected bags, sometimes referred to as multiple blood bag systems.
When closed blood bag systems were initially used, valve systems were relatively simple. Such valves were often no more than a simple external clamp or, in later versions, a small metal bead (B-B) located within a blood bag tubing but which could be externally manipulated to fall into an attached blood bag, thereby providing flow from or to the bag through the tubing.
In later years, a more positive sealing valve was needed to preclude untimely leakage between the tubing and the bag or bags. This led to the use of positive seal transverse membranes being located within the tubing as in U.S. Pat. No. 3,110,308 to Bellamy or within a "port" attached to one end of the blood bag and into which tubing was bonded as in, for example, U.S. Pat. No. 4,195,632, to Parker et al. When sealed membranes were used, it was necessary to include a means for piercing the membrane by external manipulation of a device located within the closed system. In the Bellamy patent this was done with a small, pointed cannula located within the tubing and adjacent the transverse membrane. In the Parker et al patent, a pointed vaned spike is shown.
Although the above-described positive seal valves have been in use for sometime, they are, in many cases, difficult to use because of the external pressure required to rupture the membrane. In addition, the inclusion of a cannula or a spike within the system interfered to some extent with fluid flow after the membrane had been pierced. These shortcomings, among others, have led to the development of yet another group of blood bag valves referred to as frangible valves.
As used herein, the expression frangible valve means a valve which provides a positive seal in a closed plastic bag system and which is opened by external manipulation (without entering the closed system) of the valve, typically by breaking a portion of the valve at a weakened portion in the valve itself.
Examples of frangible valves for closed blood bag systems are shown in U.S. Pat. No. 4,007,738 to Yoshino (frangible valve located in port and tubing between bags); U.S. Pat. No. 3,654,924 to Wilson et al (frangible valve in sample pouch and having same pass through inner diameter as connecting tubing); U.S. Pat. No. 4,181,140 to Bayham et al (frangible valve with lateral vanes attached); U.S. Pat. No. 4,386,622 to Munsch (frangible valve having projecting "handles" which permit the "walking" of part of the valve after breaking, along a tubing); U.S. Pat. No. 4,270,534 to Adams (frangible valve with retention flange); U.S. Pat. No. 4,294,247 to Carter et al (re-sealing frangible valve); and U.S. Pat. No. 4,340,049 to Munsch (frangible valve with "handles"). In all of the above examples, the frangible valves are located within connecting tubing or a port or, in the case of the '924 patent, within a sample pouch. In general, such valves are still difficult to externally manipulate by hand and, in most cases, the location of the valve is such that it interferes with optimum flow of blood or blood components into or out of the blood bag. In addition, such valves or closure systems commonly contain a space above the bag top which can trap red blood cells. This typically can result in the undesirable contamination of plasma and platelet preparations with those red cells.
A blood bag known as Biopack.RTM.P (available from Biotest Pharma, Dreieich, W. Germany) and a blood bag known as "Tuta Blood Donor Pack" (available from Tuta Laboratories (Australia) Pty., Ltd., Lane Cove, N.S.W. Australia) both include frangible valves having an upper portion located in a port and a lower portion extending into the bag and sealing a bore in the upper portion. Those valves are opened by externally manipulating the lower portion to break it at a weakened portion, thereby opening the valve for fluid flow. Unfortunately, the breakaway portion breaks completely free from the top portion, therefore allowing it to move freely within the blood or blood components which can partially or fully interfere with fluid flow. This is undesireable. Also, at the point of administration of the blood unit (typically in a hospital) the administering personnel inspecting the blood unit prior to transfusion may mistake the free floating plug as a gross clot or contaminant. In addition, when both valves are opened, the opening appears to be considerably less than the opening (inner cross section area) within the connecting tubing, thereby restricting fluid flow between the bag and connecting tubing. We have now developed a frangible valve for plastic bags which avoids the above-described shortcomings. Details are described below.